custom product loop

<?php
$args = array(
  'post_type' => 'product',
  'product_cat' => 'klaviere',
  'posts_per_page' => 3,
  'orderby' => 'date',
  'order' => 'DESC'
);
$loop = new WP_Query($args);
while ($loop->have_posts()) : $loop->the_post();
  global $product; ?>
  <div class="span3">
    <a id="id-<?php the_id(); ?>" href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">
      <?php if (has_post_thumbnail($loop->post->ID)) echo get_the_post_thumbnail($loop->post->ID, 'shop_catalog');
      else echo '<img src="' . woocommerce_placeholder_img_src() . '" alt="My Image Placeholder" width="65px" height="115px" />'; ?>
      <h3><?php the_title(); ?></h3>
      <span class="price"><?php echo $product->get_sale_price(); ?></span>
      <span class="price"><?php echo $product->get_regular_price(); ?></span>
    </a>
    <?php woocommerce_template_loop_add_to_cart($loop->post, $product); ?>
  </div><!-- /span3 -->
<?php endwhile; ?>
<?php wp_reset_query(); ?>